The present invention relates in general to a liquid crystal display (LCD), and more particularly, to a liquid crystal panel with improved color and brightness.
Due to the characteristics of thin profile and low power consumption, liquid crystal displays (LCDs) are widely employed in electronic products, such as portable personal computers, digital cameras, projectors, and the like. Generally, LCD devices are classified into transmissive, reflective, and transflective types. The transmissive LCD employs a backlight module as the light source. The reflective LCD employs the ambient light as the light source. The transflective LCD employs the backlight module or the ambient light as the light source.
FIG. 1 illustrates a pixel structure in a conventional liquid crystal panel and FIG. 2 is a cross-section along line 2-2 line shown in FIG. 1. The pixel structure 101 of the liquid crystal panel comprises a red sub-pixel 101R, a green sub-pixel 101G, and a blue sub-pixel 101B. Each sub-pixel comprises a lower substrate 100, a device layer 104, a liquid crystal layer 106, a color filter 103, 105, or 107, and an upper substrate 102. The device layer 104 is disposed on the lower substrate 100, which may comprise gate lines, data lines, transistors, passivation layers, and pixel electrodes. In order to simplify the diagram, only a flat layer is depicted. The upper substrate 102 is disposed opposite to the lower substrate 100. The color filters 103, 105, and 107 are disposed on the upper substrate 102 and face the lower substrate 100. The color filters 103, 105, and 107 respectively correspond to the red sub-pixel 101R, the green sub-pixel 101G, and the blue sub-pixel 101B. The liquid crystal layer 106 is disposed between the device layer 104 and the color filters 103, 105, and 107.
In order to meet the high chromaticity requirement for transmissive or reflective liquid crystal panels, the thickness of the color filter or the concentration of the pigment in the color filters must be increased. As a result, transmittance of the transmissive liquid crystal panel or reflectivity of the reflective liquid crystal panel is reduced, resulting in lower brightness. Additionally, for the transflective liquid crystal panel, since the light must pass through the color filter twice in reflective mode, higher chromaticity is obtained than transmissive mode. Moreover, brightness of the transflective liquid crystal panel may be reduced. Brightness of the transflective liquid crystal panel can be improved by increasing the area of the reflective area therein. It is useless, however, to reduce chromaticity in reflective mode. That is, the color balance problem still exists.
Since liquid crystal display technology has gradually replaced conventional cathode ray tube (CRT) technology, new pixel structures are required to improve color and brightness of liquid crystal panels to increase display quality.